Worker units have been sent to gather resources (right) and return them to the central building. Resources (recorded top right) are being
spent building an additional worker (bottom center). Dark fog (left) blocks visibility away from player units.

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knowing exactly what the other players are doing.
Similar to many board games, competitive video
games usually require adversarial reasoning to react
according to other players’ actions (Laird and van
Lent 2001; Mehta et al. 2009; Weber, Mateas, and
Jhala 2010).

RTS Games
This article is focused on real-time strategy games,
which are essentially simplified military simulations.

In an RTS game, a player indirectly controls manyunits and structures by issuing orders from an over-head perspective (figure 1) in real time in order togather resources, build an infrastructure and an army,and destroy the opposing player’s forces. The real-time aspect comes from the fact that players do nottake turns, but instead may perform as many actionsas they are physically able to make, while the gamesimulation runs at a constant frame rate ( 24 framesper second in StarCraft) to approximate a continuousflow of time. Some notable RTS games include DuneII, Total Annihilation, and the Warcraft, Command &Conquer, Age of Empires, and StarCraft series.

Generally, each match in an RTS game involves
two players starting with a few units and/or structures in different locations on a two-dimensional terrain (map). Nearby resources can be gathered in order
to produce additional units and structures and purchase upgrades, thus gaining access to more
advanced in-game technology (units, structures, and
upgrades). Additional resources and strategically
important points are spread around the map, forcing
players to spread out their units and buildings in
order to attack or defend these positions. Visibility is
usually limited to a small area around player-owned
units, limiting information and forcing players to
conduct reconnaissance in order to respond effectively to their opponents. In most RTS games, a